Christopher Persons, IERUS Technologies; Greg Finney, IERUS Technologies
Keywords: Space situational awareness, modeling, polarimetry, non-resolved object characterization
Abstract:
The Aero-Optical Prediction Tool (AerOPT) is a visible-through-LWIR atmospherics and sensor model applicable to space situational awareness (SSA) systems that employ radiometric, polarimetric, hyperspectral, and/or active components. AerOPT has been used for performance predictions, trade studies, design, and anomaly troubleshooting for optical system on a variety of programs supporting agencies such as Air Force Research Laboratory, Missile Defense Agency, National Reconnaissance Office, Space and Missile Defense Command, Army Research Laboratory, and Aviation and Missile Center.
This presentation provides a brief overview of AerOPT capabilities and gives several examples of its application. Included are the results from a local area SSA study that evaluated the utility of visible polarimetric imaging in a compact sensor that is derived from a miniature star tracker. The study concluded that polarimetric imaging provides forensic data that can be used to infer information about the state of unresolved resident space objects beyond what can be derived from radiometric data alone.
Engineers from IERUS Technologies have been involved in the development of AerOPT for the last 20+ years. AerOPT is government-purpose rights software, written in MATLAB® that produces imagery, video, and statistics at any processing step for a point source, complex target, or a complex scene provided by an external scene generator or low-noise, oversampled collected imagery. Scene generators have included Time-domain Analysis Simulation for Advanced Tracking (TASAT), Optical Signatures Code (OSC), and Fast Line-of-sight Imagery for Target and Exhaust Signatures (FLITES). AerOPT applies atmospheric turbulence with realistic spatio-temporal correlation and has the interfaces built-in for applying adaptive optic wavefront corrections. It also applies atmospheric transmission, path radiance, forward scatter and either monostatic or bistatic backscatter. Atmospheric scattering is specific to a provided distribution of aerosol sizes, while path radiance and the other sources of transmission are obtained through standard codes such as MODerate spectral resolution atmospheric TRANsmittance (MODTRAN) code and Laser Environmental Effects Definition and Reference (LEEDR).
AerOPT includes temporal, spatial, spectral, and polarimetric dependencies in all pertinent parameters. It models collection by the optics, field-dependent optical aberrations, linear or nonlinear conversion to photoelectrons, electrical crosstalk, pixelization, digitization, calibration, and processing. It also includes thermal emissions from the optics and internal camera body, as well as shot noise, Johnson noise, and read noise. AerOPT optionally models a two-point non-uniformity correction (NUC), radiometric calibration, polarimetric calibration (if applicable), and frame averaging, and may be integrated with custom processing.
AerOPT derives its name from its origin in the hypersonics community. As such, AerOPT also takes output from computational fluid dynamics software to model the effects of aerodynamics flow on a sensor systems response, capturing the effects from the mean flow, boundary layer turbulence, and window deformation. It reports resulting imagery, as well as statistics on the point spread function (PSF), including Strehl ratio, contained energy diameters, and boresight errors. These PSF statistics are also computed when analyzing systems that are exposed to unmitigated atmospheric turbulence such as those often found in ground-based SSA applications.
Date of Conference: September 14-17, 2021
Track: Non-Resolved Object Characterization